A choir (also known as chorale or chorus) is a musical ensemble of singers. Choral music, in turn, is the music written specifically for such an ensemble to perform.
A body of singers who perform together as a group is called a choir or chorus. The former term is very often applied to groups affiliated with a church (whether or not they actually occupy the choir) and the second to groups that perform in theatres or concert halls, but this distinction is far from rigid.
The term "Choir" has the secondary definition of a subset of an ensemble; thus one speaks of the "woodwind choir" of an orchestra, or different "choirs" of voices and/or instruments in a polychoral composition. In typical 18th- to 21st-century oratorios and masses, chorus or choir is usually understood to imply more than one singer per part, in contrast to the quartet of soloists also featured in these works.
A performance, in performing arts, generally comprises an event in which a performer or group of performers behave in a particular way for another group of people, the audience. Choral music and ballet are examples. Usually the performers participate in rehearsals beforehand. Afterwards audience members often applaud.
The means of expressing appreciation can vary by culture. Chinese performers will clap with audience at the end of a performance; the return applause signals "thank you" to the audience. In Japan, folk performing arts performances commonly attract individuals who take photographs, sometimes getting up to the stage and within inches of performer's faces.
Sometimes the dividing line between performer and the audience may become blurred, as in the example of "participatory theatre" where audience members get involved in the production.
Theatrical performances can take place daily or at some other regular interval. Performances can take place at designated performance spaces (such as a theatre or concert hall), or in a non-conventional space, such as a subway station, on the street, or in someone's home.